So-called iron-based alloys such as iron alloys and steels mainly comprising iron have been most extensively used as various structural metallic materials. Since materials are currently required to be lightweight and compact in all industrial fields, the structural metallic materials are also required to satisfy such demands. While attempts have been made to have the materials have high strength to meet recent technical requirements, materials merely having a high strength are likely to be insufficient in their rigidity, and some mechanical parts are barely made lightweight and compact.
These materials may be replaced with light metals for making the materials light weight. However, when the iron-based alloy is replaced with light weight alloys such as an aluminum alloy or magnesium alloy, frames and structures will be large due to the insufficient strength of the materials, failing to yield compact structures. Alternatively, the structure may be made lightweight using ceramics. However, ceramics are not suitable for structural materials due to their poor toughness in addition to their high cost. Alternatively, iron and steel materials having a high Young's modulus have also been studied by adding reinforcing particles such as ceramic particles to iron.
However, the reinforcing particles are not perfectly adhered to the iron base in the method for adding the reinforce particles. In addition, a theoretical level of the Young's modulus cannot be attained since the reinforcing particles tend to segregate at crystal grain boundaries while causing decrease of toughness because the reinforcing particles aggregated by themselves as the amount of addition of the particles is increased. Therefore, the mechanical strength of the iron-based material can hardly be compatible with fatigue strength. Since high deformation resistance due to the presence of the reinforcing particles as well as decrease of ductility due to segregation of the reinforcing particles at the crystal grain boundaries make plastic machining such as rolling difficult, it is difficult to increase toughness by plastic machining for making γ-phase grains fine. While a martensite phase has been a representative matrix of conventional high strength materials serves to increase toughness by tempering, the iron-based material cannot be expected to have a high Young's modulus as a result of dispersion of Fe3C (cementite) phases because the material inherently contains little carbon (C), and a large proportion of the carbon, if any, in the material, forms a solid solution in iron to decrease the proportion of the Fe3C (cementite) phase.
Accordingly, it is an object of the present invention to provide an iron-based alloy and a method for producing the same, wherein mechanical characteristics such as a Young's modulus, toughness and strength are maintained at high levels without adding any reinforcing particles, besides suppressing its specific gravity from being elevated while maintaining these characteristics, resulting in light weight and compactness of the material.